The invention relates to a pin tool for efficient low volume liquid transfer.
Laboratory procedures often require a specified volume of a liquid to be placed in communication with another liquid, a sample of tissue, a filter, a piece of blotter paper or the like. This liquid transfer typically is carried out with a pipette. A pipette is a small hollow tube that may have a conically tapered end. The end of the pipette can be placed in communication with a supply of liquid so that a selected volume of liquid is urged into the pipette. The pipette then is transferred to a specified destination, and liquid in the pipette is dispensed into a small receptacle, such as a microtitre plate, or onto a substrate, such as a piece of blotter paper, a filter or a sample of tissue.
Many liquid transfer systems employ a single pipette and an apparatus for sequentially moving the pipette between the fluid source and the destination. The prior art also includes apparatus with an array of pipettes mounted to a plate such that the respective pipettes are substantially parallel and such that the ends of the pipettes are substantially coplanar. The array of pipettes can be transferred in unison to the liquid source for filing. The array of filled pipettes then can be moved to the destination where the collected liquid is aspirated. Standards have been developed throughout the industry for the number of pipettes incorporated into such an array, the spacing between the pipettes in the array and the footprint dimensions for both the plate that supports the pipettes and the apparatus with which the plate cooperates for collecting and aspirating the liquid.
Pipettes are capable of dispensing liquids in amounts as small as 500 nL. However, many laboratory tests enable procedures to be performed with much smaller volumes of liquid. As a result, liquid transfer systems have been developed that rely upon pins in place of pipettes to transfer small volumes of liquid. More particularly, a pin or an array of pins is dipped a selected distance into a liquid, and then is withdrawn. A small volume of the liquid remains on the exterior of the pin. The pin or the array of pins then is transferred to the destination, and is tapped or stamped against the reservoir or substrate. The tapping or stamping of the pin causes the liquid that had remained on the exterior of the pin to xe2x80x9ctouch offxe2x80x9d. Pin tools enable much smaller volumes of liquids to be transferred, and hence pin tools lower costs associated with the liquids that are being transferred. Additionally, pin tools enable a greater concentration of analytical tests to be performed within a given amount of space.
Prior art pin tool liquid transfer systems have either been manually operative or have incorporated the pin tool integrally into the robotic apparatus. Manual pin tool liquid transfer systems are slow and systems where the pin tool is an integral part of a robotic transfer system require downtime for periodic pin cleaning. Thus, prior art pin dispensing systems have included inefficiencies that can offset the efficiencies enabled by a small apparatus and small volume liquid transfers.
The subject invention is directed to a disposable or recyclable pin tool assembly for transferring low volumes of liquid. The pin tool assembly includes a base plate for carrying an array of pins. The base plate is substantially planar and may be molded unitarily from a plastic material. The base is formed with a plurality of apertures for slidably receiving a corresponding plurality of pins. The number of pins may vary from one application to the next. However, the number of pins preferably conforms to the number and spacing of wells in a conventional multi-well source plate. Hence, arrays of apertures in the base plate preferably equal 96, 384 or 1,536 in accordance with the number of wells in a conventional source plate.
The pins are mounted in the apertures of the base to prevent side-to-side movement or wobbling of the pins in the base plate. Additionally, each pin may be formed with an enlarged head that prevents the pin from falling completely through the respective aperture in the base plate. However, slight movement of each pin along its axis is permitted.
A weight plate may be provided across the heads of the respective pins for biasing the heads of the pins toward the base plate. However, a slight movement of individual pins can be accommodated against forces of the weight plate to compensate for dimensional inconsistencies in the wells of the source plate. Hence, all of the pins can be dipped equal distances into the wells, and substantially equal volumes of liquid can be transferred.
The pin tool assembly further comprises a transition cover that covers and engages the weight plate and the base plate.
The transition cover includes an outer surface that faces away from both the weight plate and the base plate. The outer surface may be formed with engagement means for releasable engagement with a conventional pipette head. More particularly, the pipette head includes a plate with means for gripping by a robotic apparatus. The lower surface of the plate includes a standard array of frustoconical pipettes that normally could be used for transferring larger volumes of liquid. The pipettes of the pipette head are dimensioned and configured for frictional engagement with the engagement means of the transition cover. The engagement means may be internal surfaces of recesses in the transition cover. The recesses in the transition cover may correspond one-for-one with the pipettes in the pipette head. Alternatively, there may be fewer recesses than pipettes, and the specific number of recesses is selected to ensure sufficient frictional engagement forces between the pipettes and the recesses. Thus the pipette head may be urged into engagement with the transition cover so that the tapered pipettes nest in and frictionally engage the recesses in the transition cover. The pipette head then can be moved for transporting the pin tool assembly to a source plate and then to the liquid destination.
The pin tool assembly may be employed with a docking tray. The docking tray includes a bottom wall, a plurality of upstanding side walls and an open top. The spacing of the side walls conforms to proposed SBS standards/ANSI and permits the pin tool assembly to be nested in the docking tray with the pins substantially enclosed and protected. The side walls of the docking tray may be formed to define a step or shelf on which the base plate may be seated, and the distance from the step to the bottom wall of the docking tray may exceed the projecting distance of the pins. Hence, the pins are safely surrounded and enclosed by the docking tray.
The pin tool assembly and the docking tray may be nested with the pins safely enclosed by the docking tray, as explained above. The pipette head then may be moved by a robotic device so that at least certain of the pipettes are urged into the recesses in the transition cover for frictional engagement with the recesses. The robotic device then lifts the pipette head away from the docking tray and moves the pin tool assembly to the source plate, so that the pins enter the respective wells of the source plate. The pins may move relative to the base plate to ensure substantially equal insertion into the wells for all of the pins. The robotic device then lifts the pin tool assembly away from the source plate and moves the pin tool assembly toward its destination. The pins are stamped or tapped against the destination surface to xe2x80x9ctouch offxe2x80x9d or dislodge the droplets of the liquid formed on the pins. The robotic device then moves away from the destination and ejects the pin tool assembly. The ejected pin tool assembly may be placed back in the docking tray, discarded or cleaned and recycled. The robotic device then moves the pipette head toward the next pin tool assembly to repeat the process.